This invention relates to a security device for fuel which comprises a timer and a control circuit to close the main valve of a fuel pipe in the case where hazardous conditions exist as in the leakage of fuel due to a crack of the fuel pipe or in the occurrence of an earthquake. The control circuit will also periodically close the main valve at a time instant set by the timer in the case where no hazardous conditions exist, thereby to eliminate any occurrence of dangerous fuel problems.
Recently, the network for supplying gas fuel has increased and a variety of gas utensils are extensively used by consumers. Also, the gas tightness of houses has been improved by insulation, weather stripping and the like. Accordingly, dangerous problems such as gas poisoning and gas explosion caused by gas leakage may frequently occur. In order to prevent such disasters, there has been proposed in the prior art a gas leakage alarm device which provides an alarm signal in response to the leakage of gas and a security device which operates to close the main valve in the case where hazardous conditions exist. Typical are the leakage of gas or the occurrence of an earthquake. However, these devices operate only when such hazardous conditions occur. Accordingly, even if such an alarm device is used, the dangerous condition may still occur unless the user closes the main valve after receiving the alarm signal. Furthermore, even if the security device is installed, in the case of the leakage of gas in a generally gas-tight house at night, the occupants will not sense the problem when they are asleep. Thus, the conventional security device is not complete in all aspects of safety.